1. Field of the Invention
The present invention relates generally to a cordless telephone system, and more particularly to a method of setting security codes in a cordless telephone system having one or more communicating devices.
2. Discussion of the Related Art
Cordless telephone systems generally include a base unit and a handset which communicate using Radio Frequency (RF) signals. The base unit is connected to a telephone network, such as the Public Switched Telephone Network (PSTN), while the handset can be removed from the base unit and used within a predetermined range, which is limited by the RF signal strength and not cord length. The transmission from the handset to the base unit is typically on a different frequency than the transmission from the base unit to the handset, providing duplex communications.
Existing cordless telephone systems offer additional conveniences over conventional corded phones, such as mobility, and currently a convenient method of transmitting the voice of a person or speaker, referred to hereinafter as a presenter, to a telephone network to conduct a clear telephone conversation in a conference room or auditorium setting is set forth in co-pending U.S. patent application Ser. No. 09/433,530 to Carley, filed on Nov. 4, 1999, which is incorporated herein by reference. Speakerphones may of course also be used for this purpose, however, speakerphones are often less than ideal because they restrict the movement of the presenter, who may not always want to stay near the speakerphone. In addition, speakerphones will often pick-up considerable background noise in a conference room or auditorium setting.
A presenter could carry a corded telephone handset or a cordless telephone handset to transmit the presenter""s voice to a telephone network while moving around, but this is usually not practical because it substantially restricts the ability of the presenter to use his or her hands for other purposes. Additionally, the presenter""s audience cannot hear the telephone conversation when a handset is used.
Where a sound system is being used to broadcast the presenter""s speech, the system can, in theory, be connected to a telephone line, but this is often difficult, expensive or otherwise impractical. Also, a telephone jack may not be available in many auditoriums or conference rooms.
For all of the above reasons, cordless telephone systems with multiple transmitting and receiving communicating devices have been suggested. For example, a cordless telephone system may include as a transmitting device, a cordless microphone, and as receiving devices, cordless speakers, and as combination transmitting/receiving devices, a cordless headset and a sound system interface, all wishing to communicate with a common base station. In order to minimize the cost of such a cordless telephone system, each communication device is designed for relatively simple simplex RF communications. The combination transmitting/receiving devices can conceptually be treated as separate transmitting and receiving devices in one unit. Multiple receiving devices and only one transmitting device communicate with the base unit at a given time.
In maintaining a simpler, cost effective design, there is a need to synchronize the communication between multiple communicating devices and the base unit. Given the fixed amount of radio spectrum, only a relatively small portion has been allocated to cordless telephones. Cordless telephone systems operate on a selected band of a relatively few channels. The base unit and the communicating device are set to the same channel for communication. The likelihood is high that a particular location may be undesirably within the communication range of more than one cordless telephone user on the same channel. Given the relative density of urban and suburban areas, and the desirability of having a cordless phone system with sufficient communication range to allow its use within a reasonable proximity of the base unit, a number of cordless telephone users in a given neighborhood may find themselves causing RF interference with nearby cordless telephone systems. Given also the relatively small number of channels used for cordless telephones, it is also relatively simple for a person to select a channel on his cordless telephone which is the same as the channel of another user.
For these reasons, it is common to employ a security code in cordless telephone systems. Thus, in addition to selecting one of a relatively small number of channels, a cordless telephone user is able to establish a security code, much like a security code is established by persons utilizing remote control garage door openers on a common frequency. This technique guards, at least to a certain extent, against the possibility of unintentional or unauthorized access to a user""s telephone conversation.
It is desirable to set the security code in the communicating devices by temporarily bringing them into contact with the base unit. U.S. Pat. No. 4,731,813 describes a cordless telephone system in which a single security code is communicated between the base unit and the handset by modulating the charging current supplied to the handset from the base unit. However, there are additional considerations where a cordless telephone system includes multiple communicating devices, since all receiving devices must be set to a receiving security code common with the base unit and only one transmitting device may contain the same transmitting security code, which is different from the receiving security code to prevent interference with the base unit.
Therefore, a need exists for a method of setting a transmitting security code and a receiving security code, different from the transmitting security code, in remote communicating devices in a low cost cordless telephone system with multiple remote communicating devices.
It is therefore an object of the present invention to provide a method of setting a transmitting security code and a receiving security code, different from the transmitting security code, in remote communicating devices in a low cost cordless telephone system with multiple remote communicating devices.
It is another object of the present invention to provide a method of setting a receiving security code in remote receiving devices in a low cost cordless telephone system with multiple remote communicating devices so some or all receiving devices may be set to the same receiving security code as the base unit.
It is still another object of the present invention to provide a method of setting a transmitting security code in remote transmitting devices in a low cost cordless telephone system with multiple remote communicating devices so only a selected one transmitting remote communicating device and the base unit are set to the same transmitting security code.
To achieve the above objects, a method of setting security codes in a remote communicating device using a base unit in a cordless telephone system in accordance with the present invention is provided which includes the steps of bringing the remote communicating device into electrical contact with the base unit, wherein the base unit stores a transmitting security code (TC) and a receiving security code (RC), different from the TC; determining whether the remote communicating device is either a remote receiving device (RRD), a remote transmitting device (RTD), or a remote combination transmitting/receiving device (RCD); setting the remote communicating device with the RC if the remote communicating device is a RRD, or the TC if the remote communicating device is the RTD, or both the RC and the TC if the remote communicating device is the RCD, as determined above, said setting done via the electrical contact with the base unit; and verifying the RC or TC or both the RC and the TC in the RRD, RTD, or RCD, respectively, as determined above, said verifying done via the electrical contact with the base unit.
The RC is selectable at the base unit by a user, thereby setting the same selected RC each time the RRD or the RCD is set, and the TC is automatically randomized by the base unit, thereby setting a different TC each time the RTD or the RCD is set.